The chief objectives of this multicenter, phase II, double-blind exploratory study are to determine the relative antiviral activity of nucleoside analogue regimens, whether the sequence administration of ZDV and ddI affects antiviral activity (i.e., is there a priming effect with these agents?), and the relative safety and tolerance of these regimens in subjects with relatively early HIV-1 infection and CD4 cell counts > 550/mm3.